The invention relates to a damping system for damping vibrational and other noise in passenger vehicles. More particularly, the invention relates to a system that is effective to block noise and vibration, and as a heat shield.
Automobiles are by their nature very noisy machines. Engine combustion, high velocity exhaust flow, rotating bearings, rotating transmission and axle linkages, other high speed and/or high shear moving parts, and high speed tire-road contact all generate a significant amount of noise and structural vibration, particularly at high vehicle speed. All this noise can make the passenger cabin of a traveling vehicle very uncomfortable for passengers, if not unbearable.
In addition, many automobiles components that generate a substantial amount of noise also generate a substantial amount of heat, e.g., the exhaust manifold, catalytic converter, etc. These components are located in close proximity to other components which must be shielded or insulated from heat in order to ensure maximum performance and service life. In addition, the underbody (floor pan) of the automobile must be shielded from certain underbody components, the exhaust pipes and catalytic converter in particular. If unshielded, heat from the exhaust system may be conducted through the underbody into the passenger compartment, making it uncomfortable for passengers.
Many heat-source components, in addition to generating substantial quantities of heat, also are the source of significant vibration and noise. This is because many of the sources of heat (for example exhaust gases) also are sources of vibration (due to frictional forces between passing high velocity gas and pipe walls). Conventional technologies employ separate components to damp vibration/noise and to insulate or shield against heat. Otherwise, in the case of many heat-generating components, a heat shield is provided to prevent damage to adjacent components but no noise absorption/blocking means is provided, either due to weight considerations or the potential for heat damage.
Commonly, the result can be a vibratory exhaust system that is heat-shielded but has no or inadequate vibration or noise reduction means despite being a substantial noise/vibratory source. The result is that the comfort of automobile passengers in the passenger compartment is diminished because there is insufficient noise or vibration attenuation mechanism to reduce noise emanating from high temperature components such as the catalytic converter.
Conventional heat shields applied to these situations consist of either single or layered (laminate) aluminum. This material is sometimes embossed to increase the thermal protection. Another type of material that is used is an air gap heat shield, a shield that is “blown-up” to increase the thermal protection. A third technology that is used is a denim barrier with foil on one side, which has been used to try to reduce noise as well as heat. These conventional technologies all fall short of providing adequate thermal shielding at desirably low weight, and none of them provides any substantial measure of noise abatement.
There is a need in the art for a heat shield that also functions as an effective vibration and/or noise barrier. Such a heat shield preferably will be effective up to temperatures of 1250° F., and will be at least as effective, preferably more effective, at abating tonal frequencies in the range of 20-2000 Hz as conventional systems, but will weigh less.